A front fork interposed between a vehicle body and an axle of a two-wheeled vehicle to suppress a change in vehicle attitude is equipped with a fork body performing an expansion and contraction operation with a reaction force, a reservoir tank provided outside the fork body, and a cut-off valve provided in a passage communicated between the fork body and the reservoir tank (refer to Japanese Examined Patent Publication No. 57-20498 or Japanese Unexamined Utility Model Publication No. 53-151061, for example).
A front fork of this type switches between the communication and shut-off modes between a gas chamber in the fork body and a gas chamber in the reservoir tank in order to change the effective volume of the gas chamber functioning as an air spring for adjustment of the reaction force of the air spring in two stages.
Thus, the change in vehicle attitude when the two-wheeled vehicle is braked, namely, the nose dive phenomenon in which the vehicle body pitches forwards, is restrained by blocking the inflow of the hydraulic oil from the fork body to the reservoir tank by the cut-off valve to reduce the effective volume of the gas chamber to a high state of the reaction force of the air spring in the front fork.